A shock absorber is provided with an outer shell and a piston rod inserted into the outer shell, capable of going in/out. The shock absorber exerts a damping force for suppressing relative movement of the piston rod with respect to the outer shell when the piston rod is relatively moved in an axial direction with respect to the outer shell. The shock absorber is interposed between a vehicle body and an axle in a vehicle or between a cabin and the vehicle body, for example, and can suppress vibration of a vibration damping target such as the vehicle body, the cabin and the like by exerting the damping force.
Since the shock absorber is used by being exposed to an outside, dirt, dusts and mud (hereinafter referred to as “mud and the like”) can easily adhere to the piston rod. The mud and the like adhering to an outer periphery of the piston rod are scraped off by a dust seal sealing the outer periphery of the piston rod when the piston rod enters into the outer shell. However, if the mud and the like are dried and firmly adhere to the piston rod, the mud and the like cannot be sufficiently scraped off by the dust seal, and there is a possibility that deterioration of an oil seal provided on an inner side of the dust seal is promoted.
JP2000-81071A discloses protection of the piston rod from mud and the like by mounting a dust cover covering the outer periphery of the piston rod on the shock absorber.